Suprachiasmatic nucleus circadian oscillatory protein, a novel binding partner of K-Ras in the membrane rafts, negatively regulates MAPK pathway
Suprachiasmatic nucleus circadian oscillatory protein, a novel binding partner of K-Ras in the membrane rafts, negatively regulates MAPK pathway
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DOI：
10.1074/jbc.m213214200
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发表时间：
2003-04-25
影响因子：
4.8
通讯作者：
Fukada, Y
中科院分区：
文献类型：
--
作者：
Shimizu, K;Okada, M;Fukada, Y
视交叉上核昼夜节律振荡蛋白（SCOP）是富含亮氨酸重复序列（LRR）蛋白家族的一员。除了在大鼠下丘脑视交叉上核中的circathan表达外，SCOP在整个大鼠脑中的神经元中组成性表达。在这里，我们发现，大量的SCOP定位于脑膜筏，其中只有K-Ras是丰富的Ras异构体。SCOP直接通过其LRR结构域与筏组分中存在的无鸟嘌呤核苷酸形式的K-Ras子集相互作用。这种相互作用干扰了体外添加的鸟嘌呤核苷酸与K-Ras的结合。在稳定过表达SCOP或其缺失突变体的PC 12细胞系中检测了SCOP对K-Ras功能的负调节作用。过表达全长SCOP显著下调ERK 1/ERK 2激活诱导的去极化或佛波酯刺激，过表达SCOP的这种抑制作用依赖于其LRR结构域。这些结果强烈表明，SCOP负调控K-Ras信号在膜筏，确定了一种新的机制，为Ras-MAPK途径的调节。
Suprachiasmatic nucleus circadian oscillatory protein (SCOP) is a member of the leucine-rich repeat (LRR)-containing protein family. In addition to circathan expression in the rat hypothalamic suprachiasmatic nucleus, SCOP is constitutively expressed in neurons throughout the rat brain. Here we found that a substantial amount of SCOP was localized in the brain membrane rafts, in which only K-Ras was abundant among Ras isoforms. SCOP interacted directly through its LRR domain with a subset of K-Ras in the guanine nucleotide-free form that was present in the raft fraction. This interaction interfered with the binding of added guanine nucleotide to K-Ras in vitro. A negative regulatory role of SCOP for K-Ras function was examined in PC12 cell lines stably overexpressing SCOP or its deletion mutants. Overexpression of full-length SCOP markedly down-regulated ERK1/ERK2 activation induced by depolarization or phorbol ester stimulation, and this inhibitory effect of overexpressed SCOP was dependent on its LRR domain. These results strongly suggest that SCOP negatively regulates K-Ras signaling in the membrane rafts, identifying a novel mechanism for regulation of the Ras-MAPK pathway.